One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,4,6)(3,7,8,5)(12,20)(15,21)(19,24)(22,23)(25,26,31,28,30,35,29,34)(27,33,36,32,38,39,37,40)(1,3,4,8)(2,5,6,7)(9,10,13,16)(11,17,18,14)(12,21,20,15)(19,22,24,23)(25,27)(26,32)(28,33)(29,36)(30,38)(31,37)(34,39)(35,40)(2,6)(5,7)(9,11)(10,14)(12,19)(13,18)(15,22)(16,17)(20,24)(21,23)(25,27)(26,33)(28,32)(29,37)(30,38)(31,36)(34,40)(35,39) involution — undirected(3,8)(5,7)(11,18)(14,17)(19,24)(22,23)(25,28,29,26,30,34,31,35)(27,32,37,33,38,40,36,39)(9,12,13,20)(10,15,16,21)(11,19,18,24)(14,22,17,23)(25,29,30,31)(26,34,35,28)(27,36,38,37)(32,39,40,33)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.